The invention relates to a bag-filling machine in which the material to be filled is conveyed by compressed air through a filling tube. The bag-filling machine has a storage cylinder which is closed at its underside by a grid-like floor having ventilation apertures. The filling tube is fitted in the peripheral wall of the storage cylinder, above the floor.
Bag-filling machines of such a type, which operate by the pneumatic conveying principle, have been known for many years and are used for the filling of bags with dust-forming goods. The grid-like floor serves to loosen up the material to be filled by means of the air stream so that the material becomes flowable and can pass into the filling tube. It is known to construct the floor so as to be inclined downwardly relative to the filling tube in order to assure more favorable flow conditions at the transition from the storage cylinder to the filling tube. Furthermore, it is known to broaden the filling tube, which is disposed at a certain spacing above the floor, conically towards the storage cylinder so that a nozzle-like transition from the storage cylinder to the filling tube is produced.
In practice, pneumatic conveying per se has become established. Disadvantages are such that the filling tube is not completely emptied when the bag, which is controlled by a weighing machine, is filled. As a rule, the filling tube is also included in the weighing because the bag is suspended at the filling tube and cannot be weighed independently of the filling tube. This problem leads to an inaccuracy in the weighing process. This inaccuracy brings about a situation in which, by way of a precautionary measure, more material must be filled into the bag than intended. Problems also arise when changing the material to be filled, since very large residual quantities remain in the conventional type filling machines. These residual quantities must be emptied, whereby the change-over time is considerably increased.